1. Field of the Invention
The present invention relates to an image forming apparatus having a self-repair function, and more particularly, to an image forming apparatus capable of making self-diagnosis as to whether the apparatus develops a fault and making self-repair of the fault developed by the apparatus by converting detected values obtained from the apparatus into qualitative values and comparing the qualitative values obtained by the conversion with virtual cases previously found and stored.
2. Description of the Related Art
In the development field of precision instruments, industrial machines and the like, expert systems utilizing artificial intelligence (so-called AI) techniques have been studied extensively in recent years for the purpose of realizing labor saving in maintenance work and long-term automatic operation. The expert systems include one for making self-diagnosis as to whether or not an apparatus develops a fault and making self-repair of the fault developed by the apparatus.
However, the conventional expert system (an automatic control system and a fault diagnosis system) only basically operates an actuator corresponding to a sensor on the basis of an output of the sensor. Accordingly, it is not complete as a self-repair machine.
Therefore, the applicant of the present application has found a machine control method using diagnosis-repair inference on an objective model based on qualitative physics and invented a new self-diagnosis and self-repair system for an image forming apparatus utilizing such a machine control method, to file a patent application (see, for example, Japanese Patent Laid-Open Gazette No. 4-130459).
The self-diagnosis and self-repair system for an image forming apparatus according to the prior application has the following features:
(1) Detected values of sensors provided for the image forming apparatus are converted into qualitative values and the qualitative values are used for control. PA1 (2) The construction and the property of the image forming apparatus are qualitatively expressed using a cause-effect relation network of parameters (a parameter model) representing the property of the image forming apparatus. PA1 (3) The qualitative values into which the values of the sensors are converted are applied to the parameter model to make qualitative simulation for fault diagnosis and fault repair inference.
More specifically, fault diagnosis and fault repair based on the qualitative model based system (QMS) are made.
In the self-diagnosis and self-repair system according to the prior application of the applicant having the foregoing features, even if the image forming apparatus develops a fault accompanied by, for example, the change in the construction, the fault can be flexibly coped with. The reason for this is that it is possible to dynamically change a control point and a control loop of the image forming apparatus by utilizing the qualitative simulation.
In order to operate the above described self-diagnosis and self-repair system according to the prior application as a practical built-in type system, however, it is necessary to reduce the scale of the system with respect to the fault diagnosis as well as to improve the execution speed with respect to the fault repair.
As one method, the inventors and the applicant of the present application have previously proposed a control device for making fault diagnosis using knowledge of virtual cases, to file patent applications (see seven applications, that is, Japanese Patent Application Nos. 4-66439 to 4-66445). If such knowledge of virtual cases is used, that is, virtual cases are used, it is not necessary to make the qualitative simulation by applying the qualitative values obtained from the image forming apparatus to the parameter model at the time of the fault diagnosis, thereby to make it possible to separate a fault diagnosis portion and a simulation portion from each other. Accordingly, the image forming apparatus may be only provided with a fault diagnosis portion storing virtual cases. Therefore, it is possible to reduce the capacity of the system for fault diagnosis carried in the image forming apparatus.